JPH11318893A - Ultrasonic probe - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly sensitive ultrasonic probe by effectively exciting the connecting vibration of a y-direction with an x-direction in a piezoelectric vibrator. SOLUTION: Piezoelectric bodies 6 included in multiple piezoelectric vibrators 20 which are arranged in an array shape and respectively and independently driven are sliced into regular square prisms 22 in the vibrators 20. Thus, the extension/contraction of the vibrators 20 in a longitudinal direction (y-direction) is enabled like the extension of the array direction (x-direction). Therefore, a vibration mode concerning an x-z surface becomes equivalent to that concerning a y-z surface in a resonance frequency and the connecting vibration of them is excited so that the sensitivity is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe, and more particularly, to an increase in sensitivity thereof.

[0002]

2. Description of the Related Art In an ultrasonic diagnostic apparatus employing an electronic scanning system, an electronic scanning array probe having an array-type vibrator section in which a number of small rectangular piezoelectric vibrators are arranged is used. .

FIG. 4 is a schematic perspective view showing a schematic structure of a conventional linear array probe. In this conventional linear array probe, a plurality of piezoelectric vibrators 2 are fixed on a backing material 4 in alignment in the array direction. Each piezoelectric vibrator 2 has a structure in which a positive electrode 8 and a negative electrode 10 are provided on the front and back surfaces of a piezoelectric body 6 made of a material such as piezoelectric ceramics, respectively.

[0004] Lead wires (not shown) are connected to the positive electrode 8 and the negative electrode 10, and by applying a voltage pulse to the piezoelectric vibrator 2 via these lead wires, the piezoelectric body 6 vibrates. As a result, ultrasonic waves are emitted to the subject located in front of the transducer array. On the other hand, when the ultrasonic wave reflected by the subject enters the front surface of the vibrator array, the piezoelectric body 6 that resonates with the ultrasonic wave generates a voltage corresponding to the distortion due to the vibration,
This is extracted as a voltage signal between the positive electrode 8 and the negative electrode 10.

In such a conventional ultrasonic probe, a large number of piezoelectric vibrators 2 which are separated in the array direction and driven independently of each other generally include a plate of a piezoelectric body 6 connected in the array direction. After the plates (or sheets) of the positive electrode 8 and the negative electrode 10 are laminated, a cut in the slice direction is formed in the integrated laminate.

The pitch of the vibrator array is small, for example, a pitch of 0.2 mm or less is also manufactured. On the other hand, each piezoelectric vibrator 2 requires a certain amount of vibrator area for reasons such as securing the sensitivity. Therefore, the piezoelectric vibrator 2 has a dimension in the slice direction that is sufficiently larger than the dimension in the array direction, and has a rectangular planar shape.

[0007]

As described above, the conventional individual piezoelectric vibrators constituting the vibrator array are more sufficient in the slice direction (y direction) than in the array direction (x direction). Due to its long rectangular shape, its behavior was simple and one-dimensional. More specifically, when the vibrator vibrates in a direction perpendicular to the electrode surface (in the Z direction), it expands and contracts in a direction perpendicular to the electrode surface. And when it extends in the z-direction, it contracts in a direction perpendicular to it. In the conventional strip shape, the expansion and contraction in the orthogonal direction due to the vibration occurs one-dimensionally in the x direction having a small dimension relatively easily, but is suppressed in the y direction having a large dimension.

That is, in the conventional piezoelectric vibrator, y
The vibration mode in the direction is weak, and the combined vibration of the vibration in the y direction and the vibration in the x direction is hardly excited, and there is a problem in improving the sensitivity of the ultrasonic probe.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and provides a highly sensitive ultrasonic probe that effectively excites combined vibration in the y-direction and the x-direction in a piezoelectric vibrator. The purpose is to:

[0010]

In an ultrasonic probe according to the present invention, a piezoelectric material of a vibrator is formed at least at a central portion in a longitudinal direction of the vibrator by slicing in a direction perpendicular to an electrode surface. It is characterized by having one or a plurality of square prism portions.

According to the present invention, each transducer is completely divided or partially divided in the form of a groove by slicing in the direction of the transducer array in which a plurality of transducers are arranged. Due to this division, a portion in which the cross-sectional shape parallel to the transducer electrode surface is a square, that is, a structure that is a square prism is formed in the piezoelectric material constituting each transducer. The square prism structure is provided at least at the center of the vibrator in the longitudinal direction orthogonal to the vibrator array direction of the vibrator. In addition, a structure in which a regular square prism structure is arranged over the entire vibrator, that is, over the entire longitudinal direction, may be employed.

[0012]

Next, a preferred embodiment of an ultrasonic probe according to the present invention will be described with reference to the drawings. In the following drawings, the same components as those in FIG. 4 are denoted by the same reference numerals, and the description will be simplified.

FIG. 1 is a schematic perspective view showing a schematic configuration of a transducer section of an ultrasonic probe according to an embodiment of the present invention. The vibrator portion has an array structure and includes a large number of piezoelectric vibrators 20 which are arranged and fixed on the backing material 4 along the array direction (x direction) shown in the figure and which are driven independently of each other. These piezoelectric vibrators 20 are separated from each other by, for example, forming a laminated body of the integral piezoelectric body 6, the positive electrode 8, and the negative electrode 10 on the backing material 4 as in the related art, and then placing the laminated body in the array direction. Orthogonal direction (slice direction:
This can be realized by slicing in the y direction).

The piezoelectric body 6 is formed using a piezoelectric ceramic plate such as PZT. The positive electrode 8 and the negative electrode 10 are formed, for example, by depositing a metal film having a thickness of several thousand angstroms on both surfaces of the piezoelectric body 6 by a sputtering method.

Lead wires (not shown) are drawn out from the positive electrode 8 and the negative electrode 10 from the ends in the slice direction. By applying a voltage pulse to the piezoelectric vibrator 2 via these lead wires, the piezoelectric body 6 vibrates, and an ultrasonic wave is emitted to the subject located on the front surface of the vibrator array. On the other hand, when the ultrasonic wave reflected by the subject enters the front surface of the vibrator array, the piezoelectric body 6 that resonates with the ultrasonic wave generates a voltage corresponding to the distortion caused by the vibration, and this generates a voltage between the positive electrode 8 and the negative electrode 10. It is taken out as a voltage signal between them.

An acoustic matching layer for matching acoustic impedance with a living body as a subject and an acoustic lens for focusing an emitted ultrasonic beam are provided on a front surface of the piezoelectric vibrator 2. However, they are omitted in FIG.

The major feature of this probe is that each piezoelectric vibrator 2
This is because the piezoelectric element 6 has a square prism structure within 0. That is, the piezoelectric body 6 of the piezoelectric vibrator 20 is divided into, for example, five square prisms 22 in the illustrated example in the slice direction.
That is, each quadrangular prism formed by the division is formed such that the ratio (W2 / W1) of the width W2 in the y direction to the width W1 in the x direction is preferably 1, that is, the cross section is a regular square. Is done. Note that the height of the piezoelectric body 6 is shown as T.

It is desirable that the gap in the slice direction of these square prisms 22 be as small as possible.
It is formed to a thickness of about 05 mm. For example, in order to obtain strength against mechanical stress and thermal stress of the piezoelectric vibrator 20 and improve durability, a gap between the square prisms 22 is filled with a filler. This filler 2
For 4, it is desirable to use a soft material that does not hinder the expansion and contraction of each square prism 22 in the y direction. In addition, the gap between the piezoelectric vibrators 20 may be filled with an insulating filler to improve the strength. However, in FIG. The gap between them is not shown.

The square prisms 22 included in the same piezoelectric vibrator 20 are electrically connected to each other and driven by a common pulse. In other words, different piezoelectric vibrators 20 can be driven with different phases, while one piezoelectric vibrator 20
Are driven in phase with each other.

The piezoelectric body 6 of each piezoelectric vibrator 20 is
The separation into two can be achieved, for example, by further slicing the piezoelectric vibrator 20 in the array direction. If the slicing step is performed after forming an electrode (positive electrode 8 in the illustrated example) on the surface on which the slice is to be placed, the connection between the divided square pillars 22 of the divided positive electrode 8 is performed. For example, a method of filling the gap with a conductive filler may be used to recover the problem.

FIG. 2 is a graph showing the measurement results of the coupling coefficient Kt indicating the degree of coupling of the vibration of the piezoelectric body 6 having a rectangular cross section in the y direction and the x direction. In the figure, the vertical axis represents the coupling coefficient Kt, and the horizontal axis represents the ratio (W2 / W1). This measurement result shows the case where W1 / T = 0.6 and W1 = 0.33 mm. In the figure, (W2 / W1) = 1, 2, 3, 5,
The results for 6,20,40 are shown. As is apparent from the figure, when (W2 / W1) = 1, Kt exceeds the line of 0.68, while at other (W2 / W1) values, Kt is Kt.
Are all less than that. That is, the case of (W2 / W1) = 1 indicates that the coupling of the vibration in the x direction and the y direction is strong. This is because by setting the dimensions of the piezoelectric body 6 in the x direction and the y direction to be equal, the respective basic resonance frequencies or higher-order resonance frequencies in both directions become equal, and coupled vibration is excited. When the coupled vibration is excited, the vibration mode can be made larger than in the case where each of the x and y directions is independent, and the sensitivity of the piezoelectric vibrator 2 is improved.

In the example shown in FIG. 1, the square prism 22 is provided in the entire slice direction. However, a structure in which the square prism 22 is provided only at the center of the piezoelectric vibrator is also possible. FIG. 3 is a schematic plan view (FIG. 3A) showing the configuration of an example of the vibrator section of such an ultrasonic probe, and a front view of the piezoelectric vibrator 30 viewed from the array direction (FIG. b)). In the configuration shown in FIG. 3, the square prism 22 is a piezoelectric vibrator 2
The three piezoelectric vibrators 3 are provided at the center in the y direction of 0.
The portions on both sides of 0 are rectangular. With such a configuration, the sensitivity near the center in the y direction can be higher than that at the end. Further, this configuration illustrates a case where the piezoelectric body 6 is not completely separated by the slice in the array direction. For example, there is a problem in assembling, for example, when completely separating the piezoelectric body 6 may cause separation of the negative electrode 10 sandwiched between the backing material 4 and the piezoelectric body 6 in the y direction. At times, a part of the back surface of the piezoelectric body 6 may be left without being separated. In this case, the square prism 22 has a height corresponding to the slice depth in the array direction. It is preferable that the thickness of the piezoelectric body 6 left without being separated is as small as possible, for example, about 0.05 mm.

Incidentally, also in this case, the gap of the positive electrode 8 above the quadrangular prism is connected by a conductive filler. For example, after the piezoelectric body 6 is sliced in the array direction, the positive electrode 8 is formed in common on each piezoelectric vibrator 20 on the upper surface, and thereafter, the piezoelectric vibrator 20 is separated by slicing in the slice direction. According to the assembling procedure, the positive electrode 8 between the quadrangular prisms included in the piezoelectric vibrator 30 is not divided, and the necessity of using a conductive filler is eliminated.

In the above, FIGS. 1 and 3 only describe that W2 and W1 are equal. On the other hand, with respect to T, a ratio (W1 / T) that optimizes the sensitivity is conventionally selected, and W1 and T are determined based on the ratio. In other words, while only the vibration mode related to the x-axis and the z-axis has been considered in the past, the present invention combines the vibration mode of the y-axis and the z-axis with this vibration mode, so that the piezoelectric vibrator 2 This realizes high sensitivity. Therefore, in the present invention, W1 and W2 are made equal, and the influence of T is also taken into account as in the conventional case, and W1 (or W1) that gives the optimum coupling coefficient is used.
2) and T are selected.

[0025]

According to the ultrasonic probe of the present invention, by slicing the piezoelectric vibrator into a square prism, the vibration modes in two directions orthogonal to the thickness direction of the piezoelectric vibrator are coupled, and the vibration is generated. Can be excited. As a result, the piezoelectric vibrator can emit higher energy ultrasonic waves with the same voltage pulse, and can output a larger voltage signal for the same received wave at the time of reception. Is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view illustrating a schematic configuration of a transducer unit of an ultrasonic probe according to a first embodiment of the present invention.

FIG. 2 is a graph showing a measurement result of a coupling coefficient Kt indicating a degree of coupling between vibrations of a piezoelectric body having a rectangular cross-sectional shape in a y direction and an x direction.

FIG. 3 is a schematic plan view of a vibrator part of an ultrasonic probe according to a second embodiment of the present invention and a schematic front view of a piezoelectric vibrator.

FIG. 4 is a schematic perspective view showing a schematic structure of a conventional linear array probe.

[Explanation of symbols]

4 backing material, 6 piezoelectric body, 8 positive electrode, 10 negative electrode, 20 piezoelectric vibrator, 22 square prism, 24 filler.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Koichiro Fujii 6-22-1, Mure, Mitaka-shi, Tokyo Aloka Co., Ltd.

Claims (1)

[Claims] 1. An ultrasonic probe in which a plurality of strip-shaped vibrators each having a piezoelectric material between electrodes are arranged in parallel with each other and emit ultrasonic waves from the vibrators, wherein the piezoelectric material of the vibrator is An ultrasonic probe having at least a central portion in the longitudinal direction of the vibrator and one or more square quadrangular prism portions formed by slicing in a direction perpendicular to the electrode.